Cystic fibrosis epidemiology and demographics
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Epidemiology and Demographics
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Epidemiology and Demographics
Cystic fibrosis is the most common life-limiting autosomal recessive disease among people of European heritage. In the United States, approximately 30,000 individuals have CF; most are diagnosed by six months of age. Canada has approximately 3,000 citizens with CF. Approximately 1 in 25 people of European descent and 1 in 22 people of Ashkenazi Jewish descent is a carrier of a cystic fibrosis mutation. Although CF is less common in these groups, approximately 1 in 46 Hispanics, 1 in 65 Africans and 1 in 90 Asians carry at least one abnormal CFTR gene.
Cystic fibrosis is diagnosed in males and females equally. For unclear reasons, males tend to have a longer life expectancy than females. Life expectancy for people with CF depends largely upon access to health care. In 1959, the median age of survival of children with cystic fibrosis was six months. In the United States, the life expectancy for infants born in 2006 with CF is 36.8 years, based upon data compiled by the Cystic Fibrosis Foundation.
The Cystic Fibrosis Foundation also compiles lifestyle information about American adults with CF. In 2004, the foundation reported that 91% had graduated high school and 54% had at least some college education. Employment data revealed 12.6% of adults were disabled and 9.9% were unemployed. Marital information showed that 59% of adults were single and 36% were married or living with a partner. In 2004, 191 American women with CF were pregnant.
Theories about the prevalence of CF
The ΔF508 mutation is estimated to be up to 52,000 years old. Numerous hypotheses have been advanced as to why such a lethal mutation has persisted and spread in the human population. Other common autosomal recessive diseases such as sickle-cell anemia have been found to protect carriers from other diseases, a concept known as heterozygote advantage. Resistance to the following have all been proposed as possible sources of heterozygote advantage:
- Cholera: With the discovery that cholera toxin requires normal host CFTR proteins to function properly, it was hypothesized that carriers of mutant CFTR genes benefited from resistance to cholera and other causes of diarrhea. Further studies have not confirmed this hypothesis.
- Typhoid: Normal CFTR proteins are also essential for the entry of Salmonella typhi into cells, suggesting that carriers of mutant CFTR genes might be resistant to typhoid fever. No in vivo study has yet confirmed this. In both cases, the low level of cystic fibrosis outside of Europe, in places where both cholera and typhoid fever are endemic, is not immediately explicable.
- Diarrhoea: It has also been hypothesized that the prevalence of CF in Europe might be connected with the development of cattle domestication. In this hypothesis, carriers of a single mutant CFTR chromosome had some protection from diarrhoea caused by lactose intolerance, prior to the appearance of the mutations that created lactose tolerance.
- Tuberculosis: Poolman and Galvani from Yale University have added another possible explanation - that carriers of the gene have some resistance to TB.
- ↑ Rosenstein BJ and Cutting GR. The diagnosis of cystic fibrosis: a consensus statement. Cystic Fibrosis Foundation Consensus Panel. J Pediatr. 1998 Apr;132(4):589-95. Review. PMID 9580754
- ↑ Hamosh A, Fitz-Simmons SC, Macek M Jr, Knowles MR, Rosenstein BJ, Cutting GR. Comparison of the clinical manifestations of cystic fibrosis in black and white patients. J Pediatr. 1998 Feb;132(2):255-9. PMID 9506637
- ↑ Kerem B, Chiba-Falek O, Kerem E. Cystic fibrosis in Jews: frequency and mutation distribution. Genet Test. 1997;1(1):35-9. Review. PMID 10464623
- ↑ Rosenfeld, M, Davis, R, FitzSimmons, S, et al Gender gap in cystic fibrosis mortality. Am J Epidemiol 1997 145,794–803
- ↑ New Statistics Show CF Patients Living Longer. Cystic Fibrosis Foundation (April 26, 2006). Retrieved on 2007-12-09.
- ↑ Wiuf C. Do delta F508 heterozygotes have a selective advantage? Genet Res. 2001 Aug;78(1):41-7. PMID 11556136
- ↑ Gabriel SE, Brigman KN, Koller BH, Boucher RC, Stutts MJ. Cystic fibrosis heterozygote resistance to cholera toxin in the cystic fibrosis mouse model. Science. 1994 Oct 7;266(5182):107-9. PMID 7524148
- ↑ Cuthbert AW, Halstead J, Ratcliff R, Colledge WH, Evans MJ. The genetic advantage hypothesis in cystic fibrosis heterozygotes: a murine study. J Physiol. 1995 Jan 15;482 (Pt 2):449-54. PMID 7714835
- ↑ Hogenauer C, Santa Ana CA, Porter JL, Millard M, Gelfand A, Rosenblatt RL, Prestidge CB, Fordtran JS. Active intestinal chloride secretion in human carriers of cystic fibrosis mutations: an evaluation of the hypothesis that heterozygotes have subnormal active intestinal chloride secretion. Am J Hum Genet. 2000 Dec;67(6):1422–7. Epub 2000 Oct 30. PMID 11055897.
- ↑ Pier GB, Grout M, Zaidi T, Meluleni G, Mueschenborn SS, Banting G, Ratcliff R, Evans MJ, Colledge WH. Salmonella typhi uses CFTR to enter intestinal epithelial cells. Nature. 1998 May 7;393(6680):79–82. PMID 9590693
- ↑ Modiano G, Ciminelli BM, Pignatti PF. Cystic Fibrosis: Cystic fibrosis and lactase persistence: a possible correlation. Eur J Hum Genet. 2007 Mar;15(3):255-9. PMID: 17180122.
- ↑ Cystic fibrosis gene protects against tuberculosis
- ↑ Footprint fears for new TB threat
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